Lets put down some Swedish numbers.

During the coldest winter month, solar energy produce (as per statistics from the solar industry in Sweden) somewhere around 3-7% of the amount produced during the warmest month. Households also consume around 2-4 times the amount of energy during the coldest month compared to the warmest month. Sweden is a country where only a small minority have air conditioning installed at home.

Those are the worst month vs the best month. Overall the winter is not that bad, but it is still pretty bad for solar. Talking with people who has had solar installed here, the general story is very similar. During periods where it do produce the market price is already exceptional low, so it isn't returning a major saving. When the market price is high, the output is low, forcing them to be connected to the grid and pay whatever the electrical company demand during the highest market peaks, as well as taxes and grid fees which themselves has increased to match the cost of high variability.

All this looks very different in countries with much warmer climates and where the major energy consumption from households are air conditioning.

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kalleboo a day ago | parent | next [-]

The nice thing is Sweden has lots of hydro, which works as natural long-term energy storage. Every bit of solar you generate means water is kept in the dam for use later in the year.

You also can't ignore wind power which should be part of any plan to "overbuild".

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mastermage a day ago | parent | next [-]

All of the discussions here conveniently ignore the existance of Wind. Which fortunately has higher yield in the months when there is less sun.

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TheOtherHobbes a day ago | parent [-]

Yes, it's a mix. It's always a mix. Arguing that "renewables" = "solar" is a classic straw man.

So is comparing rooftop solar for a single property to grid solar for a country to a continent-sized grid of mixed renewable sources.

Battery and storage tech are barely getting started. Pumped storage is perfectly capable of smoothing out seasonal loads.

There's some capex for physical pumped storage - less than for a nuke plant - but once running it's comparatively low cost.

	▲	fi358 a day ago \| parent [-]
		I think the amount of energy needed during wintertime would be difficult to cover with pumped storage or traditional batteries. You have to have suitable geography for pumped storage and also enough (fresh) water available for that. However, instead of water compressed air could be also used, but that has also problems.

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mpweiher a day ago | parent | prev [-]

So why are the Swedes investing heavily in nuclear energy again, after nixing the nuclear exit they had on the books?

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ViewTrick1002 a day ago | parent [-]

Sweden isn't investing in nuclear power. The current right wing government is creating a culture war issue while not wanting to accept the costs, nor creating a deal that will survive through elections by creating a more comprehensive coalition backing it.

They've moved "We'll start building this electory cycle!!" to "large scale reactors" to "SMRs!!" to now targetting the final investment decision in 2029.

The latest step in the saga is the state owned power company refusing to get their credit rating tarnished by being too involved in the nuclear project. The latest move is them owning 20%, the industry owning 20% and the government owning 60%.

The industry still haven't comitted to their 20% due to the absolutely stupid costs involved.

With the government as a first negotiation move stepping in with a direct handout of €3B. On top of credit and construction guarantees, a CFD and adjusting it all depending on how costly the build is to guarantee a profit.

But it is quite easy to understand why. Taking what one of the nuclear reactors earns in Sweden and then applying solely the interest from a new build leads to a loss of ~€1.5B per year. Then you also need to run, fuel and maintain the plant.

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mpweiher 5 hours ago | parent [-]

Reality does not seem to want to conform to your creative confabulations.

"Once committed to phasing out nuclear power, Sweden has reversed course, not only lifting the ban on new reactors but also introducing government frameworks to accelerate investments and deployment.

Today, Sweden’s nuclear roadmap includes commissioning two large-scale reactors to add 2.5GW of capacity by 2035 and the equivalent of 10 new reactors, with a push for smaller modular reactors (SMRs), by 2045. According to GlobalData, the country is on course to reach 8.2GW in nuclear capacity and 59.8TWh in annual generation by 2035." -- Inside Sweden’s policy U-turn: Q&A with the Government’s nuclear lead

https://finance.yahoo.com/economy/policy/articles/inside-swe...

"Nuclear, onshore wind cheapest way to meet Sweden's electricity needs, OECD report says

If nuclear builds become more expensive or electricity imports cheaper, "there might be an opening for offshore wind to enter Sweden's optimal capacity mix", the report said. "For the time being, this is not the case."" -- https://uk.finance.yahoo.com/news/nuclear-onshore-wind-cheap...

"Nordic governments are pushing ahead with nuclear energy investments at a pace not seen in decades, driven by growing anxiety over energy security and the need to cut carbon emissions. " -- https://www.msn.com/en-us/politics/government/nordic-countri...

"Sweden’s nuclear landscape has done a 180-turn in recent years, moving from plans for a phase-out now to ambitions for an expansion. The government has lifted the reactor cap, opened new sites and introduced measures to accelerate investments and deployments.

The country’s nuclear roadmap now includes adding at least 2.5GW of capacity by 2035 and the equivalent of 10 new reactors by 2045." -- https://www.msn.com/en-us/money/other/new-episode-q-a-with-s...

"Application submitted for Swedish SMR plant

Monday, 23 March 2026

Kärnfull Next has submitted an application to build a power plant based on small modular reactors in the municipality of Valdemarsvik in Östergötland county in southeastern Sweden. It is the first application under the country’s new Act on Government Approval of Nuclear Facilities." -- https://www.world-nuclear-news.org/articles/application-subm...

"Sweden Reverses Nuclear Phase-Out, Plans Major Expansion by 2045

According to a report from Power Technology, Sweden has reversed its nuclear energy policy in recent years, abandoning previous phase-out plans in favor of expansion. The national government has removed a cap on the number of reactors, designated new locations for plants, and implemented policies to speed up related investment and construction. The current national strategy aims to increase nuclear power capacity by a minimum of 2.5 gigawatts by 2035. A further goal is to build new reactors with a combined capacity equal to ten standard units by 2045." -- https://www.indexbox.io/blog/sweden-reverses-nuclear-phase-o...

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ViewTrick1002 4 hours ago | parent [-]

Like I told you. A culture war issue without broader political backing, with the company putting final investment decision at such a timing in terms of election cycles as to ensure that broad political backing is there, or it won’t happen.

The social democrats opened up to negotiate a broader energy agreement covering both nuclear power and off-shore wind.

The right and hard right shut down that effort because only tens of billions in handouts per new built large scale reactor in capacity is the only solution. Even mentioning off-shore wind is a red like for them.

It is truly interesting when the right becomes the socialists. But that’s were we are in 2026.

Also, go ahead and please explain how Sweden can have 2.5 GW online by 2035 when investment decision is set to 2029 and projects like the Canadian SMF, French EPR2 and Polish AP1000 have similar dates as their ”perfectly executed project target date”, likely ending up being late 2030s or early 2040s?

It’s always funny when you proclaim imaginary new built nuclear power as the solution, rather than staying grounded in reality.

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mpweiher 3 hours ago | parent [-]

Cope harder.

Once again: your fantasies that you present as facts have nothing to do with reality.

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ViewTrick1002 3 hours ago | parent [-]

These are all facts. Why are you so afraid of renewables and storage?

Translate with your favorite tool:

https://www.svt.se/nyheter/inrikes/m-och-sd-gjorde-karnkraft...

	▲	mpweiher 40 minutes ago \| parent [-]
		None of the things you claimed are facts. None.

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grey-area a day ago | parent | prev | next [-]

Scotland at a similar latitude to the populated parts of Sweden has hit 100% renewables generation in the past and will do so again.

Renewables are not just solar and hydro storage is also suitable.

You are also ignoring that improving housing stock with good insulation is a much better answer to excessive energy use in winter than attempting to find more supply in winter.

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gpm a day ago | parent | prev [-]

Yeah but:

1. Sweden is just about the worst case, there's very few countries/people that far north.

2. There's this genius invention called "wires". HVDC has transmission losses on the order of 3.5% per 1,000km. You don't have to colocate the solar.

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nnevod 6 hours ago | parent | next [-]

HVDC (and even the grid in general) doesn't transmit all that much power. The largest currently existing line - Changji-Guquan UHVDC link in China - transmits 12GW. It's significantly more than what an average long-range link of current grids transmits, yes. But is it a lot?

Looking from consumption side, my home city of ~1 million people has several coal-fired plants, producing 1.5 GW of electricity and about 5GW of heating. Plus an hydropower station producing 6 GW. Most of that is consumed by an aluminium plant, but nonetheless, it's also part of the city. So that's roughly 12GW on a cold winter day (I suppose we do want to make heating cleaner as well), and probably 6 GW in summer. Heat pumps could be used to reduce power consumed by heating, but even the air-source pumps are not cheap, and they don't provide much efficiency gain in the cold. Ground-source pumps are extremely expensive and reqiure heat replenishment or the ground will freeze - such is the balance here.

So, the world's largest link to power just one city, out of tens of them. It quickly gets prohibitively expensive.

The only realictic answer, it seems, is annual-scale storage. I hope that "dirt pile storage" works well enough and succeeds, batteries are just too expensive and material hungry, hydrogen is problematic to store well either and we don't seem to have good enough scalable direct carbon capture to synthesize methane or propane.

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AnthonyMouse a day ago | parent | prev | next [-]

> Sweden is just about the worst case, there's very few countries/people that far north.

Sweden is worse but it's still a significant issue in e.g. New York or Paris or Auckland.

> There's genius invention called "wires". HVDC has transmission losses on the order of 3.5% per 1,000km. You don't have to colocate the solar.

It's more than 1000km from the places that get cold to a part of the world where it isn't winter.

Suppose we ignore that it's winter in the US Northeast and Southeast at the same time and run HVDC 2000+ km to Florida because it gets an extra hour of sunlight. Long distance transmission can't be used to counter seasonal output and regional weather at the same time because one requires the generation to be spread everywhere and the other requires it to be concentrated closer to the equator. If we concentrate the solar in Florida to mitigate winter in New England then we're screwed when Florida is overcast.

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gpm a day ago | parent [-]

> it's still a significant issue in e.g. New York or Paris or Auckland.

No it isn't.

Wires still might be worth it, but these are all close enough to the equator that you can just over provision locally without issue if you prefer.

> It's more than 1000km from the places that get cold

Solar panels work better in the cold. The issue is with how far from the equator Sweden is, not how cold it is.

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AnthonyMouse a day ago | parent [-]

> No it isn't.

In the US Northeast solar generates around four times as much in July as December. This is sufficiently bad when what you need is more power in the winter. Paris is a little worse. Sweden is significantly worse.

> Wires still might be worth it, but these are all close enough to the equator that you can just over provision locally without issue if you prefer.

If I need 25% more output in the month when solar has 75% less output, how much do I have to over-provision?

> Solar panels work better in the cold.

Places that need more electricity in the winter because they're cold are cold in the winter because they're further away from the equator.

	▲	gpm a day ago \| parent [-]
		> This is sufficiently bad when what you need is more power in the winter. Nope, it isn't. Solar is cheap and the costs are continuing to fall quickly. Generating 5x more power in the summer than needed is perfectly fine and just a nice added bonus. Wires are probably a good idea to reduce that number, but with how solar panels are dropping in price traditional forms of electricity generation (nuclear, fossil fuels, etc) just won't be competitive at that multiplier even without them. > Places that need more electricity in the winter because they're cold are cold in the winter because they're further away from the equator. Temperature has a lot to do with ocean currents. NY and Sweden overlap in how cold they are (taking the right parts of both). The southernmost point of Sweden is at 55.3 degrees north, the northermost point of NY is at 45.0 degrees north. They aren't even close to overlapping in how far north they are.

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belorn a day ago | parent | prev | next [-]

Wires and HVDC transmissions are nice, but they have a fairly large downside. They are major infrastructure projects that cost a lot of money and they don't produce any energy. Adding that cost to the solar panels makes them significantly more expensive, and solar/wind farms owners are not exactly willing to bear that cost.

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buzer a day ago | parent | prev [-]

You don't need to colocate the solar, but you need to make sure you can get that power when you actually need it.

During crisis nations are going to restrict exporting electricity and prioritizing their own residents. Electricity that is generated in Germany is not going to warm up Nordic countries if Germany doesn't let it.

Wires are also susceptible to sabotage, especially undersea ones (which are the current major connection points to Europe).

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hardlianotion a day ago | parent [-]

The issue is more the other way at the moment. Norwegian prices can get high as they are exposed to German demand over the interconnector.

	▲	buzer a day ago \| parent [-]
		Sure, that is the current situation but if the Nordic countries started relying on solar from central Europe (especially Finland since it doesn't have the hydro capacity Norway & Sweden have) things could get ugly during crisis. The GP essentially framed overprovisioned solar as solution to anyone who might rely on nuclear without taking in account realities in many countries.